The research proposal outlined will investigate cellular responses to environmental stresses that include infection by viral pathogens. Viruses target cellular metabolic pathways in a number of ways, to inhibit the ability of the host to respond to infection, characteristics of which are exhibited by plant viruses, including geminiviruses. Characterization of the mechanisms by which plant viruses inactivate these defenses will be of considerable use for the development of disease resistance strategies to human and plant viral pathogens. These studies will characterize metabolic pathways that respond to stress, and determine the function of viral genes in altering antiviral responses by using a plant viral system which offers several advantages, including the ability to easily transform and regenerate plant tissue, short generation times and the ability to generate large numbers of stably transformed progeny in a very short time period, and the presence of evolutionarily conserved metabolic pathways. The Arabidopsis AKIN11 gene codes for a serine/threonine protein kinase homologous to the mammalian AMP-activated protein kinase (AMPK), a central regulator of metabolic pathways in mammals. These kinases are broadly conserved in eukaryotes and are central components of cascades that function in regulating responses to stresses that deplete cellular ATP levels, including nutrient starvation, hypoxia, exercise, heat shock and viral infection. The observation that viral proteins interact with and inactivate AKIN11 implies that viruses have evolved mechanisms to alter evolutionarily conserved metabolic pathways to evade antiviral defenses, The specific aims of this project will be achieved by taking four approaches. Cellular factors targeted by geminiviral genes and the cellular AKIN11 gene will be identified using differential display and cDNA array technologies. The role of AKIN11 in responding to stress will be characterized by mutational analysis of the promoter elements to define regions that respond to external stimuli. The role of viral RNA in suppression of host viral defenses will be determined by identifying elements required for RNA polymerase III transcription and using transgenic plants to analyze the effect of a non-coding RNA on viral infectivity.